Conventional combustion burners typically employ a configuration to stabilize the outer flame of combustion flame. In this configuration, a high-temperature and high-oxygen area is formed in an outer peripheral part of the combustion flame, resulting in an increase in the emission amount of NOx. As an example of such conventional combustion burners employing this configuration, a technology described in Patent Document 1 is known.
[Patent Document 1] Japanese Patent No. 2781740